For readers who may have been lost in detail...
in general terms...
Electric pumps almost always have less flow than eng driven devices.They are capable of full pressure but flow rates are much less therefore for hi flow devices pressure will drop markedly.
Engines, even if not operating in flt will in most cases have sufficient power to generate hyd pressure if still selected on , pump is OK and fluid level sufficient.Witness how quickly hyd pressure comes up during starter ops prior to light off.